Machines for reproducing flat keys exist which comprise a rotary cutter and a follower, these two elements being adapted to be displaced simultaneously in two orthogonal directions. These machines are often used to reproduce a key of which a model is available and which is fixed in front of the follower. In this case, the follower scans the notches of the model key; the cutter then cuts notches which are identical to those of the model key, into a blank fixed in front of it.
These machines may also be used for reproducing a key of which only the code number is known. In this case, up to the present time, mother-keys or matrices are used, which comprise notches spaced apart from one another by a distance equal to the spacing between the notches of the key to be produced, all these notches having the same depth in a given matrix; one matrix exists for each figure of the code, i.e. for each possible depth for a notch. A matrix corresponding to the first figure of the code is fixed in front of the follower and the follower is engaged in the first notch of this matrix so as to cut the first notch in the blank. This matrix is then replaced by a second matrix corresponding to the second figure of the code and the follower is engaged in the second notch of this matrix so as to cut a second notch in the blank. This operation is continued successively for all the figures of the code.
However, this method is not satisfactory. After each notch has been cut, a matrix must be repositioned, which is complicated and a source of error. Furthermore, a determined notch of the matrix, and only this notch, mut be scanned by the follower. This operation is delicate; if the follower slips, the cutter forms a notch of incorrect shape and the blank being cut must be scrapped. This latter drawback may be overcome by providing one matrix per depth and per possible location of notch, but, in that case, the number of matrices is considerably increased; there is always a source of errors due to the repositioning of a matrix after each notch is cut.
Machines also exist in which a blank is cut notch by notch with the aid of a cutter having the shape of the notch, by displacing the blank clamped in a vice longitudinally and transversely in front of the cutter. However, if the type of key is changed, the cutter must be changed, which is a difficult and delicate operation. Moreover, the operator must calculate the displacements of the vice as a function of the code of the key, which is a source of errors.